A system and apparatus for monitoring the thickness of a sample under test

Abstract

The application discloses a kind of to be measured sample thickness monitoring system and device, including based on system controller drive stage movement to preset station, the preset station is based on prior knowledge suitable for the position coordinates of to be measured sample thickness monitoring;Light source is used to irradiate the stage, at least one pair of images before and after the stage is carried to be measured sample is obtained by corresponding detector arranged in another end of the stage respectively, and pixel position marking processing is carried out to the obtained image;And based on the multiple images after marking processing are carried out deviation calculation, determine the relationship between to be measured sample thickness and deviation value, to be measured sample thickness monitoring method is simple, device is simple;Easy fast detection whole piece to be measured sample maximum thickness, high precision;For different topography to be measured sample good applicability.

Description

Technical Field

[0001] This invention belongs to the field of imaging analysis technology, and specifically relates to a system and device for monitoring the thickness of a sample under test. Background Technology

[0002] Using high-magnification and high-numerical-aperture objectives can improve detection resolution, but the working distance is shorter, which may lead to collisions with the sample. When the sample is too thin, the objective will not be able to focus on the sample surface; when the sample is too thick, the risk of collision between the objective and the sample increases. Therefore, monitoring the thickness of the sample becomes very important.

[0003] Existing methods for measuring the thickness of samples employ optical detection systems. The surface of the sample to be measured has multiple measurement areas. Light from the sample (such as a wafer) is directed into the detector according to specific requirements. This approach cannot quickly monitor the maximum thickness of the entire sample surface, has low adaptability, and leads to increased risk of collisions with short-distance objectives and reduced production efficiency.

[0004] In view of this, the present invention provides a system and apparatus for monitoring the thickness of a sample to be tested. Summary of the Invention

[0005] To overcome the problems in the prior art, this invention proposes a sample thickness monitoring system and device. Parallel light is used to illuminate the sample stage, causing a portion of its shadow to be projected onto a detector. The detector obtains shadow images of the stage before and after the sample is mounted. The sample thickness is determined based on the shadow movement distance. By rotating the stage, the maximum deviation distance of the shadow image is recorded, which represents the maximum thickness of the entire sample. According to one aspect of this invention, a sample thickness monitoring system is provided, comprising the following steps:

[0006] The device controller drives the stage to move to a preset station, which provides suitable position coordinates for monitoring the thickness of the sample based on prior knowledge.

[0007] The stage is illuminated by a parallel light source, and at least one image is acquired before and after the sample is placed on the stage using detectors located at the other end of the stage. The acquired images are then marked with pixel positions.

[0008] Based on the multiple images after the labeling process, deviation calculation is performed to determine the relationship between the thickness of the sample to be tested and the deviation threshold.

[0009] As a preferred embodiment of the present invention, a point light source is lit up, and the scattered light emitted by the point light source passes through a collimating lens to form a parallel light source. The point light source includes, but is not limited to, one or more combinations of LED point light sources and single optical fiber filaments.

[0010] As a preferred embodiment of the present invention, the sample to be tested includes, but is not limited to, a wafer.

[0011] As a preferred embodiment of the present invention, the detector includes, but is not limited to, a camera.

[0012] As a preferred embodiment of the present invention, when the stage carrying the sample to be tested is located at the preset work position, the light source beam passes parallel to the geometric center of the sample to be tested.

[0013] As a preferred embodiment of the present invention, the deviation calculation step includes:

[0014] Acquire a first image of the stage carrying the sample to be tested, and calculate the pixel position X1 of the shadow boundary line of the image; rotate the stage carrying the sample to be tested at a preset angle, and the detector acquires a second image; calculate the pixel position X2 of the shadow boundary line of the acquired multiple second images, which deviates most from X1; and

[0015] Calculate the deviation threshold X, where the deviation value X is equal to the difference between X2 and X1.

[0016] As a preferred embodiment of the present invention, the preset angle is marked as a;

[0017] Where a = 50D / R, D is the beam diameter, R is the radius of the sample to be measured, and the preset angle is less than or equal to 180° until the rotation angle of the stage exceeds 180°.

[0018] According to another aspect of the present invention, a sample thickness monitoring device is provided, based on the implementation of the sample thickness monitoring system, comprising a stage and a sample to be tested placed on the stage, characterized in that...

[0019] According to the position of the sample to be tested, a point light source, a collimating lens, and a detector are set up parallel to each other along a straight line.

[0020] A point light source and a collimating lens are set parallel to each other on one side of the stage;

[0021] The collimating lens collimates the light from the point source, and the collimated light rays are parallel to the stage before entering the detector.

[0022] A detector, arranged parallel to the other side of the stage, captures a sample shadow image of the stage and the sample to be tested. According to another aspect of the invention, an electronic device is provided, comprising: a processor and a memory, wherein the memory stores a computer program that can be called by the processor;

[0023] The processor executes a sample thickness monitoring system by calling a computer program stored in the memory.

[0024] The beneficial effects of this invention are that the method for monitoring the thickness of the sample to be tested provided by this invention is simple and the device is basic; it can quickly and easily detect the maximum thickness of the entire sample to be tested with high accuracy; and it has good applicability to samples with different morphologies. It facilitates self-inspection of the thickness of the sample to be tested inside the defect detection machine, reduces the risk of sample collision, improves production efficiency, and is applicable to samples with different morphologies without requiring customized solutions. Attached Figure Description

[0025] The above and other objects, features, and advantages of exemplary embodiments of the present invention will become readily apparent from the following detailed description taken in conjunction with the accompanying drawings. Several embodiments of the invention are illustrated in the drawings by way of example and not limitation, wherein:

[0026] Figure 1 An architecture diagram of an optical inspection system for inspecting samples;

[0027] In the figure: 101, stage; 102, sample to be tested; 103, objective lens; 104, light source; 105, second optical element; 106, beam splitter; 107, tube lens; 108, first optical element; 109, detector.

[0028] Figure 2 A thickness monitoring system framework diagram according to one embodiment of the present invention;

[0029] In the figure: 201, stage; 202, sample to be tested; 203, point light source; 204, collimating lens; 205, detector; 206, objective lens.

[0030] Figure 3 A sample shadow map for thickness monitoring according to one embodiment of the present invention.

[0031] Figure 4 A schematic diagram of a thickness monitoring system according to one embodiment of the present invention. Detailed Implementation

[0032] The different figures in the embodiments are described below.

[0033] Figure 1 It is an optical detection system structure in which the surface of the sample to be tested has multiple test areas. Figure 2 This is a framework diagram of a thickness monitoring system according to one embodiment of the present invention. Figure 3 This is a sample shadow image for thickness monitoring according to one embodiment of the present invention, wherein, Figure 3 (a) In the shadow map obtained by the detector before the sample to be tested is mounted, pixel position X1 represents the stage height information. Figure 3(b) The image is taken after the stage rotates 180 degrees to support the sample. Pixel position X2 represents the height information of the stage and the sample. The difference between X2 and X1 represents the maximum thickness information of the sample.

[0034] The structure of the optical inspection system is as follows Figure 1 As shown, the optical inspection system includes a sample to be inspected 102, a stage 101, a first light source 104, a beam splitter 106, a first optical element 108, a second optical element 105, an objective lens 104, a tube lens 107, and a detector 109. The sample to be inspected 102 can be a wafer or a substrate.

[0035] The stage 101 is used to support the sample 102 to be tested, and the sample 102 has multiple test areas on its test surface.

[0036] The first light source 104 may include broadband light sources and other suitable light sources, such as broadband plasma light sources and various lasers;

[0037] The second optical element 105 is used to control parameters such as the light intensity, wavelength, and angle of the emitted light from the light source 104. The second optical element 105 includes, but is not limited to, a spectral filter, a polarizer, and an aperture element.

[0038] The detector 109 is used to acquire a detection image of the area to be measured. The detector 109 includes any type of sensor for optical detection and measurement, including but not limited to CCD sensors, CMOS image sensors, line sensors or time-delay integration TDI sensors, etc., and can also be photodiodes, photomultiplier tubes or single-photon detectors.

[0039] The first optical element 108 can be a filter, polarizer, apodizer, homogenizer, beam shaper, or other components, so that light from the sample 102 (wafer) under test enters the detector 109 according to the corresponding requirements.

[0040] The stage 101 can move along a predetermined path so that multiple test areas on the test surface are sequentially located within the system's field of view in a predetermined order.

[0041] Example 1

[0042] Please see Figure 2 As shown, this embodiment of a sample thickness monitoring device includes a stage 201 and a sample 202 placed on the stage 201.

[0043] According to the position of the sample 202 to be tested, a second light source 203, a collimating lens 204 and a detector 205 are arranged parallel to each other along a straight line; indicating that the second light source 203, the collimating lens 204, the sample 202 to be tested and the detector 205 are on the same horizontal line.

[0044] The second light source 203 is arranged parallel to one side of the stage 201;

[0045] It should be noted that the second light source 203 includes, but is not limited to, LED point light sources and light sources connected to the first light source 104 via optical fibers.

[0046] The collimating lens 204 collimates the light from the second light source 203, and the collimated light rays are parallel to the stage 201 and enter the detector.

[0047] It should be noted that the light emitted by the second light source 203 is adjusted by the collimating lens 204 to obtain parallel light rays, which illuminate the sample 202 under test, reducing the influence of light and shadow.

[0048] The stage 201 is used to support the sample 202 to be tested, and can move in the X, Y and Z directions and rotate at any angle.

[0049] The sample to be tested 202 is placed on the stage 201, and the sample to be tested 202 includes, but is not limited to, a wafer;

[0050] Detector 205 is arranged parallel to the other side of stage 201 to capture sample shadow images of stage 201 and sample 202 to be tested. Detector 205 can be a camera.

[0051] It should be noted that this embodiment is used to measure the thickness of a wafer non-contactly. By analyzing the sample shadow image, the thickness information of the wafer can be obtained without physical contact with the wafer surface, which helps to prevent contamination or damage to the wafer.

[0052] The second light source 203 and collimating lens 204 ensure that the light rays illuminate the sample 202 under test in parallel, which helps to produce clear shadows. When the sample 202 is illuminated, it will produce shadows. These shadows will be projected into the detector 205, which can capture the shadow images of the stage 201 and the sample 202 under test. Then, by rotating the stage 201, the maximum thickness of the sample 202 under test can be found, which is helpful in ensuring the quality and specifications of the sample 202 under test.

[0053] By comparing the shadow images of the sample 202 at different locations, the distance the shadow moves can be measured. This distance is related to the thickness of the sample 202. By measuring the distance the shadow moves, the thickness of the wafer can be estimated; the thicker the wafer, the greater the distance the shadow moves.

[0054] Rotating stage 201 records the maximum deviation distance: By rotating stage 201, the maximum thickness of the wafer can be found because the shadow moves the greatest distance at this angle.

[0055] and Figure 1 Compared with existing technologies, it can be seen that the optical detection element used in this embodiment is simpler, does not require complex optical path control, is easier to implement and maintain, and obtains a clear shadow image based on the second light source 203 and collimating lens 204. It is suitable for high contrast and is more suitable for applications that require high-speed detection, such as detecting surface defects or precise measurement.

[0056] However, if there are higher requirements for the sample 202 under test, or if adjustments are made under conditions of multiple light source changes, it is obvious that... Figure 1 The optical detection system structure used in this study is more suitable.

[0057] Example 2

[0058] like Figure 4 As shown, parts not described in detail in this embodiment are described in Embodiment 1. A sample thickness monitoring system is provided, including the following steps:

[0059] S1: Move the stage 201 to the preset workstation;

[0060] It should be noted that the preset station is the area used to monitor the thickness of the sample 202 under test, ensuring that the beam passes parallel to the center of the wafer. Specifically, this is achieved through offline calibration, as the beam aperture is generally large, such as 20mm, to determine whether the beam passes through the geometric center of the wafer. The stage is moved, and when a parallel beam is observed passing through the wafer center, this position is taken as the preset station. The maximum thickness of the wafer can be measured when it rotates one revolution.

[0061] S2: Control the second light source 203 to light up, and the detector 205 obtains the first shadow image of the stage 201, such as Figure 3 As shown in (a), the boundary line pixel position of the first shadow image of the stage 201 is calculated, and the boundary line pixel position of the first shadow image is recorded as X1;

[0062] S3: The robot arm places the sample 202 to be tested onto the stage 201 and uses vacuum adsorption to fix the sample 202 to be tested, so as to ensure that it is stably located on the stage.

[0063] S4: The stage 201 is set. After the stage 201 rotates at a preset angle, the detector 205 obtains the second shadow image of the stage 201, such as... Figure 3 As shown in (b), the boundary line pixel position of the second shadow image of the stage 201 is calculated, and the boundary line pixel position of the second shadow image is denoted as x. i ;

[0064] The preset angle is 'a', where 'a' = 50D / R, D is the beam diameter, and R is the wafer radius. The preset angle is less than or equal to 180° until the rotation angle of the stage 201 exceeds 180°.

[0065] S5: Calculate and mark the pixel position where the second shadow image deviates the most from x1 as X2;

[0066] S6: The deviation value X between the pixel position with the largest deviation in the second shadow image and the pixel position of the boundary line of the first shadow image is determined. The deviation value X is equal to the difference between X2 and X1. It is then determined whether the deviation value meets the set deviation threshold.

[0067] S7: If the deviation threshold requirement is met, proceed with the test sample 202 detection process; if not, an alarm will be triggered, indicating that the thickness of the test sample 202 does not meet the detection requirements; complete the test sample thickness monitoring.

[0068] The purpose of this embodiment is to monitor wafer thickness variations by analyzing the shadow images of the wafer edge using optical methods. By measuring the position of the wafer edge at different angles, it is possible to determine whether the wafer thickness meets manufacturing requirements, thereby ensuring product quality and production consistency.

[0069] It should be noted that the shadow method used in this embodiment for measuring wafer thickness has relatively low accuracy, with errors potentially reaching tens of micrometers. It is not suitable for applications requiring extremely high precision. However, it has advantages in measurement speed, especially in situations requiring high-speed monitoring of different types of wafer thicknesses. The shadow method is relatively flexible and can adapt to different types of wafers without requiring large-scale adjustments or changes. In situations requiring objective lens collision protection, its fast measurement speed allows for rapid monitoring of wafer thickness, avoiding collisions between the objective lens and the wafer, thus improving equipment safety and operational efficiency.

[0070] In short, while the shading method has lower accuracy, it remains valuable in certain specific applications. For situations requiring rapid measurement of overall wafer thickness with less stringent accuracy requirements, the shading method may be a suitable choice. However, for applications demanding higher accuracy, other measurement methods may need to be considered, such as confocal measurement or laser triangulation, which offer very high accuracy, potentially reaching sub-micron levels, but have limited measurement speed and adaptability.

[0071] It should be understood that in the embodiments of the present invention, the term "and / or" is merely a description of the relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Furthermore, the character " / " in this document generally indicates that the preceding and following associated objects have an "or" relationship.

[0072] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A sample thickness monitoring system, characterized in that, Includes the following steps: The system controller drives the stage to move to a preset station, which is a position coordinate suitable for monitoring the thickness of the sample to be tested based on prior knowledge. The stage is illuminated by a light source, and at least one image is acquired before and after the sample is placed on the stage using a detector located at the other end of the stage. The acquired images are then marked with pixel positions. Pixel position X1 represents the stage height, pixel position X2 represents the height of both the stage and the sample, and the difference between X2 and X1 represents the maximum thickness of the sample. Based on the multiple images after the labeling process, deviation calculation is performed to determine the relationship between the thickness of the sample under test and the deviation value; the deviation calculation step includes: Acquire the first image of the stage carrying the sample to be tested, and calculate the pixel position X1 of the shadow boundary line of the image; The stage, carrying the sample to be tested, rotates at a preset angle. The detector acquires a second image. The position X2, the pixel position with the largest deviation from X1 in the shadow boundary line of the acquired second image set, is calculated. Calculate the deviation value X, which is equal to the difference between X2 and X1; The preset angle a = 50D / R; Where D is the beam diameter, R is the radius of the sample to be measured, and the preset angle is less than or equal to 180° until the rotation angle of the stage exceeds 180°.

2. The sample thickness monitoring system according to claim 1, characterized in that, The light emitted by the light source passes through the collimating lens to form a parallel light source, which includes an LED point light source and a single optical fiber.

3. The sample thickness monitoring system according to claim 1, characterized in that, The sample to be tested includes a wafer.

4. The sample thickness monitoring system according to claim 1, characterized in that, The detector includes a camera.

5. The sample thickness monitoring system according to claim 1, characterized in that, When the stage carries the sample to be tested at the preset position, the light source beam passes parallel to the geometric center of the sample.

6. A sample thickness monitoring device, based on the implementation of a sample thickness monitoring system according to any one of claims 1-5, comprising a stage and a sample to be tested placed on the stage, characterized in that, According to the position of the sample to be tested, the light source, collimating lens, and detector are arranged parallel to each other along a straight line. The light source and collimating lens are set parallel to each other on one side of the stage; The collimating lens collimates the light from the light source, and the collimated light rays are parallel to the stage and enter the detector; The detector is positioned parallel to the other side of the stage to capture the sample shadow image of the stage and the sample to be tested.

7. An electronic device, characterized in that, include: A processor and a memory, wherein the memory stores a computer program that can be called by the processor; The processor executes the sample thickness monitoring system according to any one of claims 1-5 by calling the computer program stored in the memory.

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